Next generation network (NGN), which adopts IP and other packet technologies as a bearing network technology to merge fixed-line communications with mobile communications, is a hot research topic in the current field of communication standards. NGN can provide richer multimedia services which require a communication network to provide efficient end-to-end quality of service (QoS), such as emerging services having requirements on real time (e.g. video conferencing, multimedia distance learning and video on demand); meanwhile, the requirements of customers on the QoS of networks become higher and higher, therefore, how to provide end-to-end QoS becomes one of the core problems of NGN.
ITU-T is the telecommunication standardization sector of international telecommunication union (ITU) which defines standards for resource admission control. The functional frame of resource and admission control functions (RACF) is provided in the latest RACF draft released by ITU-T in May, 2008. As shown in FIG. 1, the RACF is composed of two parts which are a policy decision functional entity (PD-FE) and a transport resource control functional entity (TRC-FE).
The PD-FE, which relates to neither transmission technologies nor service control functions (SCF), makes a final decision on resource admission control according to a network policy rule, service information provided by the SCF, transport-layer subscription information provided by network attachment control functions (NACF) and a resource availability decision result provided by the TRC-FE.
The TRC-FE, which has no relationship with services but does with transmission technologies, takes charge of collecting and maintaining transmission network information and resource state information. After receiving a resource request from the PD-FE, the TRC-FE enforces resource-based admission control according to QoS, priority demands, resource availability information and transmission-related policy rules.
A transport layer consists of a policy enforcement functional entity (PE-FE) and a transport resource enforcement functional entity (TRE-FE). The PE-FE is a packet-to-packet gateway, which may be located between a customer premises network (CM) and an access network, between an access network and a core network, or between different operator networks and serves as a key node to support dynamic QoS control, port address translator control and network address translator (NAT) traversal. The TRE-FE enforces the transport resource policy rule distributed by the TRC-FE, with the range and the function thereof as well as an Rn interface remaining to be studied further, and the study is beyond the research range in R2 stage.
The PD-FE is a policy decision functional entity, which makes a preliminary QoS resource decision based on media stream session information (acquired from the SCF via an Rs interface) and the transport resource subscription information of a customer (acquired from NACF via an Ru interface), then interacts with the TRC-FE to determine whether there is enough QoS resource, and finally makes a final admission decision and distributes the admission decision to the PE-FE to be enforced.
The TRC-FE mainly takes charge of resource control, monitors resources in a network and collects related information, and makes a response according to specific resource condition when the PD-FE requests resources.
The PE-FE mainly carries out policy control (e.g. gate control, bandwidth, traffic classification and identification, traffic shaping, second-layer and third-layer QoS mapping and resource usage information collection and report) under the direction of the PD-FE.
A TRE-FE protocol is currently defined to implement a second-layer policy under the direction of the TRC-FE, with specific function and range undetermined.
In a roaming scenario, NGN is divided into a home network and a visited network. FIG. 2 is a diagram of RACF in a roaming scenario in existing technologies, in which a home location policy decision functional entity (PD-FE (H)) in a home network exchanges information with a visited location policy decision functional entity (PD-FE (V)) in a visited network via an Ri interface, and the SCF interacts with the PD-FE (H). A user equipment (UE) accesses the network at the visited location to request to use the SCF provided by the home location.
Currently, in a roaming scenario, the problem that how a PD-FE (H) in a home network cooperates and coordinates with a PD-FE (V) in a visited network to make a QoS policy remains to be solved.
FIG. 3 is a flowchart of resource admission control in a roaming scenario in existing technologies, including the following steps:
301, a UE initiates a service request and sends a request message to SCF to trigger the SCF to generate a resource initialization request;
302, the SCF sends a service request message to a PD-FE (H);
303, the PD-FE (H) first carries out an authorization check on the service request, including validating whether the requested QoS resource is accordant with a local operator policy rule and customer subscription information that is from NACF; if the authorization check is passed, the PD-FE (H) makes a resource policy decision on the service request message according to the customer subscription information, the local operator policy rule and so on, and generates a resource request message;
304, the PD-FE (H) sends a PD-FE (V) a resource request message in which QoS policy information made by the PD-FE (H) is contained;
305, the PD-FE (V) carries out an authorization check on the resource request, including determining whether the resource request is accordant with a local operator policy rule, if yes, the PD-FE (V) accepts the request and proceeds to the next step, otherwise, it rejects the request;
306, the PD-FE (V) interacts with a TRC-FE (V) to check resource availability information;
307, the PD-FE (V) makes a final resource admission decision according to the QoS policy information requested by the PD-FE (H), the resource availability information which is used as a response from the TRC-FE (V) and other information;
308, the PD-FE (V) distributes a policy rule to a PE-FE (V), and the PE-FE (V) performs a policy installation;
309, the PD-FE (V) sends a resource request response message to the PD-FE (H
310, the PD-FE (H) sends a service request response message to the SCF;
311, the SCF sends a service request response message to the UE.
In the step 305 of existing technologies, the PD-FE (V) passively processes the resource request message from the PD-FE (H), that is, since there is no negotiation mechanism between the PD-FE (V) and the PD-FE (H), the PD-FE (V) only accepts or rejects the resource request message, generally making no modification on the QoS policy information contained in the received resource request message, thus lowering the success possibility of resource requests.